In this project – using an in vivo examination of hen’s eggs composition – the effect of egg composition on the hatchability, on the chick’s hatching weight, body composition, growth and slaughter characteristics was studied. Altogether 1.500 hens’ eggs were measured by TOBEC, and the extreme and average 15-15% were chosen for incubation based on the measured E-values. During the incubation period, it was observed that eggs with high E-value/egg weight ratio fall out in a significantly higher ratio, than eggs with low E-value/egg weight ratio. Examining the separate effect of egg weight and egg composition on the hatching weight, it was established that the increase of E-value/egg weight ratio at the same egg weight, and the increase of egg weight at the same E-value/egg weight ratio resulted in an increase in the hatching weight. It was also established that the dry matter, protein and fat content of the chicks, hacthed from eggs with low electrical conductivity was higher at hatching, than that of the chicks hatched from eggs with high electrical conductivity. At 6 weeks of age the liveweight of chicks hatched from eggs with low electrical conductivity was higher in both sexes, than that of the chicks hatched from eggs with high electrical conductivity. At slaughter – at 42 days of age – significant differences were obtained in the weight of the examined body parts, but no significant effect of egg composition was observed in their ratio to liveweight.